This paper examines the environmental effects associated with Mexico's participation in the North American Free Trade Agreement (NAFTA). The objective is to provide quantitative estimates of carbon dioxide (CO₂) emissions from changes in the level and structure of production and consumption activity in Mexico following a liberalization of trade. The quantitative analysis was performed using input-output methods with fuel use modifications to account for CO₂ emissions before and after NAFTA's implementation. As a result of NAFTA, CO₂ emissions are expected to increase from the anticipated increase in the size of the Mexican economy. While total emissions increase as a result of tariff elimination, there is also a shift in the structure of production and final consumption away from those sectors that are the most C02 intensive.